In a communications system, a spectrum is divided into different frequency bands. For example, 40 available frequency bands are obtained through division in a Long Term Evolution (Long Term Evolution, LTE) system, where 777 MHz to 787 MHz is a frequency band with the sequence number of 13 (band 13 for short), 746 MHz to 756 MHz is a frequency band with the sequence number of 14 (band 14 for short), and 2300 MHz to 2400 MHz is a frequency band with the sequence number of 40 (band 40 for short). For another example, one of industrial, scientific, and medical frequency bands (ISM frequency bands) shared by each country is a frequency band from 2.4 GHz to 2.5 GHz (2.4 G frequency band for short). The frequency band is adjacent to the band 40 of the LTE system. Wireless networks such as a wireless local area network, Bluetooth, and ZigBee are all capable of working on the frequency band. For another example, a global positioning (Navigation Satellite Timing And Ranging Global Position System, GPS) system may work at 1575.42 MHz. The frequency band is adjacent to a harmonic of the band 13/band 14.
In the prior art, if a user equipment (User Equipment, UE) uses the LTE system on a certain frequency band and uses another system on a frequency band adjacent to the frequency band at the same time, sending a signal of the LTE system by the UE may interfere with the UE receiving a signal of the another system, and sending a signal of the another system by the UE may also interfere with the UE receiving a signal of the LTE system.